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On the Use of Manganese Dioxide in the Generation of 

 Oxygen from Potassium Chlorate. 



By R. R. Ramsey. 



The statement is sometimes made in texts on chemistry that the 

 part played by manganese dioxide in the generation of oxygen from 

 potassium chlorate is one of conduction only, that any other oxide, or 

 ordinary sand, which would come in intimate contact with the potas- 

 sium chlorate, would do as well. Since the black oxide, although not 

 expensive, is more expensive than sand, the use of sand would to 

 some extent diminish the cost of oxygen when generated from potas- 

 sium chlorate. 



To test this point Prof. Foley and the writer, at the suggestion 

 of the former, made the experiments as described below. 



The potassium chlorate, mixed with a detinite proportion of blacR 

 oxide or other material, was placed in an ordinar.v sheet-iron generating 

 retort which was heated with a large Bunsen burner. The oxygen 

 was led through a lead pipe coiled inside a calorimeter. From the 

 calorimeter it passed through an experimental gas meter' reading to 

 10 c.c. By this means the total volume of oxygen generated and th>^ 

 generating rate could be determined directly, and from the rise of tem- 

 perature of the contents of the calorimeter the approximate temperature 

 of the gas could be determined. Experiments were made with man- 

 ganese dioxide, pow.dered silica, sand, and Venetian red.* In no case 

 except with the manganese dioxide, did the amount of gas given off 

 compare with that computed from the chemical formula. In fact the 

 rate of generating, when using sulistances other than manganese dioxide, 

 was so slow that calorimetric determinations could not be made. Th*^ 

 following table Avill give a general view of the results: 



*Equal parts iron oxiJe .ind cTleium sulphate. 



